Field of the Invention
The invention is directed to a power conversion technique and more particularly, to a power conversion apparatus with power saving capability and high conversion efficiency.
Description of Related Art
Power conversion apparatuses are indispensable parts of electronic apparatuses at present. In a power conversion apparatus controlled based on pulse width modulation (PWM), a secondary side thereof typically includes a rectification diode. Due to the rectification diode in an on state having greater power consumption, a synchronous rectification (SR) transistor with a lower turned on resistance (Rds-on) is adopted in replacement with the rectification diode. Under such architecture, an SR controller is further needed to control the turning on and turning off of the SR transistor at the secondary side.
Generally, a parasitic capacitor is between a gate terminal and a source terminal of the SR transistor. When the SR transistor is switched between on and off states, the SR controller has to charge or discharge the parasitic capacitor, such that power consumption occurs. Besides, the SR transistor itself also consumes power. When a load of the power conversion apparatus is in a light load status, the power consumption causes reduction to conversion efficiency of the power conversion apparatus, which is unfavorable for power saving. Therefore, how to improve the overall conversion efficiency of the power conversion apparatus effectively becomes an important subject to the power conversion technology related field.